The use of plate, bolt, and nut conveyor belt fasteners, for attaching together ends of conveyor belts so that they form a closed loop, has been commonplace in mining for many years, as indicated by U.S. Pat. Nos. 1,382,799 and 1,659,001 to G. E. Purple. Typically, such fasteners are made of an upper and lower plate which are connected by bolts and nuts, plus a metal clip to retain the bolt on the bottom plate as it is positioned to the belt. The metal clip of the prior art may have wings designed to spring off the bottom plate as the bolts are tightened. As one example, see plate 21, 22, 24 of FIG. 3 of U.S. Pat. No. 1,659,001.
In another system of a belt fastener, Julen et al., U.S. Pat. No. 5,599,131 discloses a belt fastener having upper and lower plates and bolts in which the bolts are retained in their respective lower plate apertures by washers disposed on the bolt shanks. The washers are made of plastic to deform on tightening and fill in the spaces between the bolts and the lower plate. It is desirable for the bolts to be secured in the lower plates prior to assembly without falling out or rotating.
By this invention, an improved system for conveyor belt fasteners is provided, which does not have to use plastic, rubber or nylon washers which must be soft enough to deform during the assembly process to retain the bolt, and may not function well in very cold or extremely hot temperature. Also, metal assembly clips, when installed on the lower plate, can become “sprung” or loose during the original assembly process or as the bolts are being inserted into the pre-punched holes in the belt.
If special bolts are used, the basic cost will be higher than for standard designs. Assembly and swaging processes, known to the prior art, require costly mechanical equipment and often a significant labor cost. Usually, swaged assemblies are more rigid, and may be more difficult to install in pre-punched holes during field belt splicing operations.
In the prior art, to prevent bolt rotation, bolt heads are trimmed to form grooves. The lower plate is coined in a press to form projections in the groove area so that the bolt head grooves become engaged with the lower plate projections, to prevent the bolt from rotating during the nut tightening process.
It would be desirable to have a technique for preventing bolt rotation that is easier to manufacture and to handle. It would also be desirable to have a simpler way of retaining the bolts in their apertures of the lower plate before the nuts are applied to the bolts, so that they do not fall out, to facilitate the assembly of the belt fastener with the belt ends retained between the two plates.